Structures

ABSTRACT

In a lifting or load-supporting structure for use in work on high voltage installations there is provided a boom formed wholly or part by a tubular beam made of material of high electrical insulation, which beam is provided with sheds on the outside and partitions dividing the bore into a plurality of voids. Preferably such a boom is formed of a plurality of insulating elements nested together.

United States Patent [72] lnventors Carl A. Smith Dudley; John Sidney Thomas Looms, East Molesey; Cyril Harold Arthur Ely, Effingham Junction, England [21] App]. No. 770.229 [22] Filed Nov. 15, 1968 [45] Patented Jan. 12, 1971 [73] Assignees Simon Engineering Dudley Limited Queens Cross, Dudley Worcestershire, England, and Central Electricity Generating Board, London, England, a British company and a British body corporate,

respectively [32] Priority Nov. 17, 1967 [33] Great Britain [31] No. 52502/67 [54] STRUCTURES 18 Claims, 10 Drawing Figs.

[52] U.S. Cl n 182/46, 182/22174/150 511 lnt.Cl B66fl1/04 [50] Field ofSearch 182/46, 2, 141;2l2/l7, 144; 174/150 [56] References Cited UNITED STATES PATENTS 3,043,394 7/1962 Hall 182/2 3,087,581 4/1963 Pitman.... 182/2 3,213,948 10/1965 Eckels 182/2 FOREIGN PATENTS 1,513,125 l/l968 France 174/150 Primary Examiner-Reinaldo P. Machado Alt0rney-Holman & Stern ABSTRACT: In a lifting or load-supporting structure for use in work on high voltage installations there is provided a boom formed wholly or part by a tubular beam made of material of high electrical insulation, which beam is provided with sheds on the outside and partitions dividing the bore into a plurality of voids. Preferably such a boom is formed ofa plurality ofinsulating elements nested together.

PATENIEU JAN 1 2 m:

' sum 1 or 2 I i l- 778; 67.4.5017! ernL PATENIED JAN? 2 I97! SHEET 2 0F 2 STRUCTURES This invention relates to insulated booms and to lifting or loadssupporting apparatus comprising an insulated boom. Said lifting or load-supporting apparatus may comprise a relatively movable boom which may be mounted on a mobile base which boom may be a rigid unit, or an articulated unit comprising a plurality of boom elem nts which are pivotally connected in series and arranged for movement between a contracted condition and an extended condition, or a telescopic type unit comprising at least one extensible boom element.

An object of the invention is to provide an insulated boom of high electrical resistance even under adverse weather conditions.

According to the invention a boom-for a lifting or load-supporting structure is wholly or in part a tubular beam made of material of high electrical insulation and having on its outer surface a plurality of axially spaced coaxial sheds and having within its bore and substantially at right angles thereto a plurality of axially spaced bore closure members to divide the bore into a plurality of voids.

The tubular beam may comprise an insulating structure fonned of a plurality of conical insulating elements which are nested in axial alignment as described in application 800/65. Alternatively, the nested elements may have a cross-sectional shape which is oval or elliptical or triangular or rectangular or polygonal or any other convenient shape. Preferably, it is the outer end portion of the boom which is of insulating material, which outer end is provided with an attachment for lifting or supporting a load. The attachment may be a hook member, or an adjustable clamp unit or a working platform or cage to carry workmen.

When using a working platform or cage there is normally provided a linkage in the form of rods extending along the booms and arranged to keep the cage level during movement of the booms, which movement is controlled from the cage by a control rod linkage leading from the cage. These levelling and control rods include insulating elements and preferably said insulating elements are provided with sheds.

Embodiments of the invention will now be described with reference, by way of example, to the accompanying drawing, in which:

FIG. 1 is a perspective view of an articulated insulated boom arrangement mounted on a vehicle, in accordance with the invention;

FIG. 2 is an enlarged perspective view from another angle of the insulated portion of the outer boom of FIG. 1;

FIG. 3 is a partly sectioned perspective view of nested insulating elements from which the insulated portion of the boom is constructed;

FIGS. 4, 5 and 6 show other cross-sectional shapes for the nested insulating elements;

FIG. 7 shows the insulated portion of the boom provided with a lifting hook;

FIG. 8 shows the insulated portion of the boom provided with a motorized lifting winch;

FIG. 9 shows an extensible boom having an insulating outer section; and

FIG. 10 shows a telescopic tower arrangement having an insulating top section.

Referring to FIG. 1, a lifting or load-supporting structure for use in maintaining or erecting high voltage installations such as power lines comprises a movable boom 10 in accordance with the invention, which boom is pivotally connected in series with an inner boom 11 to provide an articulated structure arranged for movement between a contracted condition and an extended condition by means of hydraulic rams 12 and 13. This articulated structure is mounted on a turntable 14 on a vehicle 15 and arranged to support, at the outer end of the in sulated tubular boom part 16 of the said outer movable boom 10, a pivotally mounted working platform 17 which may be of resin-bonded fibre material of high electrical insulation or of conducting material which is to be maintained at the potential of the occupant and any supply line on which he may be workmg.

The working platform 17 is maintained in a horizontal condition irrespective of movement of the articulated booms I0 and 11 by a levelling linkage principally formed of rods 18 and 19 of which rods 18 include insulating portions 20 which are provided with sheds 21 and which extend along the insulating portion 16 of the boom. The insulating portions 20 of the levelling rods and the sheds are of high insulating material, such as resin-bonded fibre. The sheds 21'serve to eject rain and also to extend considerably the surface length of the insulation and the creepage path of any moisture film which might tend to form on the surfaces of the linkage in wet or high moisture weather conditions, such as mist or fog. The fact that the creepage path is extended by the sheds reduces the leakage current and enables the high insulating resistance provided by the structure to be maintained even under adverse weather conditions. Conveniently there are l6 sheds per rod giving an added surface length per shed of approximately 2% inches (6.35 cm).

As previously mentioned the movement of the booms is controlled by hydraulic rams l2 and I3 and also the turntable 14 is rotated by a hydraulic motor (not shown), which rams and motor are controlled by hydraulic valves mounted on the conductive portion of boom 10 and operated by insulating control rods 22 from control levers 23. Preferably the control rods are also provided with sheds 24.

The insulating part 16 of the boom 10 is formed of a plurality of nested insulating elements 25, each of which is of frustoconical shape, as shown in FIG. 3. At the narrower end, the element is completely closed by a flat portion 26 which lies normal to the axis of the element. At the wider end there is provided a flange 26a which acts as the shed. The wall thickness of the element is substantially uniform and is chosen together with the cone angle so that, when the elements are nested each element enters about halfway into the next and is secured with adhesive cement. The angle of the cone is acute and the wall thickness is small compared with the axial length so that there is a substantial void 27 between that element and the next in the nest. Preferably, the axial spacing of the elements when they are nested is more than three times the wall thickness. 7

FIG. 4 shows part of a boom formed of nested insulating elements 28, similar to those shown in FIG. 3 but having a square or rectangular cross section.

FIGS. 5 and 6 similarly show insulating elements 29 and 30 of triangular and elliptical cross section respectively. Insulating elements of any desired cross section may be selected to suit any particular mechanical characteristics provided they are tapered to nest together. FIG. 7 shows the insulated end 31 of a boom which acts as a crane jib having a plain hook 32 secured at the outer end. The inner end of the boom may be supported by other booms such as in the articulated arrangement shown in FIG. 1. The movement of the hook is effected by movement of the boom or booms.

If desired, the plain hook 32 may be replaced by a mo torized winch 33, as shown in FIG. 8. The winch may be electrically or hydraulically operated.

As a further alternative the lifting winch may be at the base and a rope or chain of insulating material passing over a pulley supported at the outer end of the insulated section of the boom, may be used to raise and lower the hook.

FIG. 9 shows an extensible boom which may be articulated with other booms or secured directly to a turntable on a vehicle or the like. The boom comprises an insulating portion 34 of the kind already described and having an inner end 35 adapted to ride on and be supported from a boom portion 36. A hydraulic ram 37 moves portion 34 relative to portion 36 thereby varying the overall length of the boom as required.

FIG. 10 shows a lifting or load-supporting structure comprising a movable boom 40 in accordance with the invention which boom 40 is the furthest extending boom element of a plurality of telescopic coaxial boom elements 41, 42 arranged to form an axially extensible tower structure which may be mounted on a vehicle. The upper end 43 of boom 49 is an insulating portion of the kind already described and supports a working platform 44 made of resinbonded fibre material of high electrical insulation, which working platform is furnished with means for controlling the telescopic movement of the extensible tower structure, which controlling means may comprise insulated control linkages of the kind already described.

lt is to be noted that he beam construction described above provides an insulating beam of high structural strength relative to its weight so that the insulating portion itself is able to withstand considerable structural forces, e.g. such as are provided by bending and like stresses.

We claim:

l. A boom for a lifting or load-supporting structure formed at least in part by a tubular beam made of material of high electrical insulation and having on its outer surface a plurality of axially spaced coaxial sheds and having within its bore and transverse thereto a plurality of axially spaced bore closure members to divide the bore into a plurality of voids, wherein the beam is formed of a plurality of insulating elements nested together in axial alignment.

2. A boom as claimed in claim 1, wherein each element comprises a tubular portion tapering in an axial direction, the narrower end of which is completely closed by an end member extending substantially at right angles to the axis of the tubular portion and forming said bore closure member, and the wider end of the element having a flange which provides one of the sheds in a nested assembly.

3. A boom as claimed in claim 2, wherein the tubular portion is of circular cross section.

4. A boom as claimed in claim 2, wherein the tubular portion is of oval or elliptical cross section.

5. A boom as claimed in claim 2, wherein the tubular portion is of rectangular cross section.

6. A boom as claimed in claim 2, wherein the tubular portion is of triangular cross section.

7. A boom as claimed in claim 2, wherein the wall thickness of each element is small compared with the axial length and the axial spacing of the elements when nested is more than three times the wall thickness.

8. A boom as claimed in claim 2, wherein each element enters about halfway into the next and is secured with an adhesive.

9. A boom as claimed in claim 1, wherein the outer end of the boom supports a load-supporting means.

10. A boom as claimed in claim 1, wherein the outer end of the boom supports a lifting means.

11. A boom as claimed in claim 1, comprising an outer insulating portion slidably supported on an inner portion so as to form an extensible boom.

12. A boom as claimed in claim 1, adapted to form the furthest extending boom of a plurality of telescopic coaxial booms of an axially extensible tower structure.

13. A lifting or load-supporting structure comprising a boom as claimed in claim 1.

14. A load supporting structure comprising a boom as claimed in claim 1, wherein the boom supports a load-supporting means which is maintained level with movement of the boom by a levelling linkage including an insulating rod element adjacent the insulating portion'of the boom.

15. A load supporting structure as claimed in claim 14, wherein the insulating rod element of the levelling linkage is provided with sheds.

16. A load supporting structure as claimed in claim 14, wherein the movement of the boom is controlled from the load supporting means through the intermediary of control rods, each including an insulating portion.

17. A load supporting structure as claimed in claim 16, wherein the insulating portion of each control rod is provided with sheds.

18. A lifting or load-supporting structure as claimed in claim 13, wherein the insulating boom is the outer boom of a boom structure, mounted on a turntable carried on a vehicle. 

1. A boom for a lifting or load-supporting structure formed at least in part by a tubular beam made of material of high electrical insulation and having on its outer surface a plurality of axially spaced coaxial sheds and having within its bore and transverse thereto a plurality of axially spaced bore closure members to divide the bore into a plurality of voids, wherein the beam is formed of a plurality of insulating elements nested together in axial alignment.
 2. A boom as claimed in claim 1, wherein each element comprises a tubular portion tapering in an axial direction, the narrower end of which is completely closed by an end member extending substantially at right angles to the axis of the tubular portion and forming said bore closure member, and the wider end of the element having a flange which provides one of the sheds in a nested assembly.
 3. A boom as claimed in claim 2, wherein the tubular portion is of circular cross section.
 4. A boom as claimed in claim 2, wherein the tubular portion is of oval or elliptical cross section.
 5. A boom as claimed in claim 2, wherein the tubular portion is of rectangular cross section.
 6. A boom as claimed in claim 2, wherein the tubular portion is of triangular cross section.
 7. A boom as claimed in claim 2, wherein the wall thickness of each element is small compared with the axial length and the axial spacing of the elements when nested is more than three times the wall thickness.
 8. A boom as claimed in claim 2, wherein each element enters about halfway into the next and is secured with an adhesive.
 9. A boom as claimed in claim 1, wherein the outer end of the boom supports a load-supporting means.
 10. A boom as claimed in claim 1, wherein the outer end of the boom supports a lifting means.
 11. A boom as claimed in claim 1, comprising an outer insulating portion slidably supported on an inner portion so as to form an extensible boom.
 12. A boom as claimed in claim 1, adapted to form the furthest extendinG boom of a plurality of telescopic coaxial booms of an axially extensible tower structure.
 13. A lifting or load-supporting structure comprising a boom as claimed in claim
 1. 14. A load supporting structure comprising a boom as claimed in claim 1, wherein the boom supports a load-supporting means which is maintained level with movement of the boom by a levelling linkage including an insulating rod element adjacent the insulating portion of the boom.
 15. A load supporting structure as claimed in claim 14, wherein the insulating rod element of the levelling linkage is provided with sheds.
 16. A load supporting structure as claimed in claim 14, wherein the movement of the boom is controlled from the load supporting means through the intermediary of control rods, each including an insulating portion.
 17. A load supporting structure as claimed in claim 16, wherein the insulating portion of each control rod is provided with sheds.
 18. A lifting or load-supporting structure as claimed in claim 13, wherein the insulating boom is the outer boom of a boom structure, mounted on a turntable carried on a vehicle. 